For the purposes of monitoring, data collection or handling, an identification label is attached to a product or other object, and the data on the ID label are read using e.g. a portable reader device such as a data collecting terminal.
In prior-art devices, the read operation in the reader device is usually initiated by pushing the appropriate button on the reader device, which button may be trigger-shaped, for example. The user either keeps the button depressed for the whole duration of the read operation, or the read operation is programmed to remain active for a predetermined time after the user has pressed the button. It is awkward for the user if he must press the push-button of the reader device in order to initiate the read operation. For example, when picking products from storage for transportation and when distributing products during transportation, it is more convenient for the user that his hands are free for handling boxes and goods instead of having to constantly press the reader push-button or key with his finger to start and/or stop the read operation.
It is also known from prior art that the user may start the reader device by giving a voice command through a microphone in the reader device to a voice recognition unit so that the read operation starts in the read unit in a known manner. Even though a voice command system frees the operator's hands, he must be careful all the time so that the voice commands are correctly given and at the right moment in relation to the positions of the reader device and the object to be read. For example, when handling goods, boxes and other such objects during a collection and packaging process, the user must not let his senses relax at any point of the read operation so that the process progresses smoothly and without errors.
Especially during an inventory, a great number of various product codes has to be read so that starting the read operation through a push-button or voice command becomes very laborious and the worker may start to feel tired in the middle of the operation. Special operations such as pressing the start button or giving a voice command slow down the progress of inventory, collection and packaging processes.
A radio-frequency (RF) reader device is capable of reading the RF signals of RF ID tags (antenna and transceiver circuit) on objects located within its reading range also without specifically starting a read operation through a push-button or voice command. Then, however, the RF reader device reads all the RF signals of the objects within its reading range whereby the operator of the reader device cannot in any way direct the read operation to certain desired goods or objects only. In inventory, collection and packaging processes as well as in distribution and other goods handling applications it is specifically important that the objects to be read can be selected as desired.